1. Field of the Invention
This invention relates to computer-interleaved barrier screen and lenticular autostereography.
2. Background of the Invention
The present invention is a modification of the autostereographic method and apparatus disclosed in U.S. Pat. No. 5,113,213, which is incorporated by reference herein (the '213 patent).
In the invention described in the '213 patent, the number of images and pitch of the resultant autostereogram are related to the resolution of the hardcopy output device by the following formula: ##EQU1##
Where pitch is the number of lines per unit of the completed autostereogram, resolution is the number of pixels per unit available from the hardcopy output device, and images is the number of images in the autostereogram.
Since images must be an integer not less than 2, there are only a finite number of possible resolutions. For example, if a hardcopy output device has a resolution of 16 pixels/mm (406.4 pixels per inch), 13 images yields a pitch of 31.26 lines per inch. Twelve images yields a pitch of 33.87 lines per inch. Other pitches, such as 32 lines per inch, are then unavailable without changing the resolution of the hardcopy output device.
This is illustrated in simplified form in FIG. 1. FIG. 1 shows that a device having an output resolution of 15 pixels per inch, and a pitch of 3 lines per inch, requires 5 images. In FIG. 1, each pixel is labeled according to which image (image 1, 2, 3, 4 or 5) it represents.
This is a severe limitation, especially when it comes to working with lenticular material. Such material must be created to exactly match one of the pitches available on the desired hardcopy output device. This is far more expensive and time consuming than using available lenticular material, which is unlikely to match the available pitches.
A second limitation arises from the loss of resolution and light from the use of large numbers of images with a parallax barrier. Even in the ideal case, the barrier screen blocks (N-1) of the N images at each location. The more images that are used, the less light is transmitted. The percent of light transmitted by a barrier screen image is also related to the resolution of the hardcopy output device by the following formula: ##EQU2##
For 13 images, 7.7% of the light is transmitted by the barrier screen. This is an acceptable amount of light for most applications. However, if 100 images are required at the resolution discussed above, the pitch for 100 images would be 4.064 lines per inch, and the amount of light transmitted by the barrier screen would be only 1%, which is unacceptable. Because many applications, e.g. animation, require 100 or more images, this is an important limitation.
A third limitation of the invention disclosed in the '213 patent arises from the output of images having a selected edge of the interleaved images aligned with the printing direction of the hardcopy output device. Although in many cases aligning the image with either the rows or the columns of the image is advantageous, this may be a significant limitation in certain cases, e.g., if the number of images required for a particular application is different from the ratio of the resolution to the pitch, or if the desired pitch is not available according to the formula given above for the pitch in a '213-type autostereogram.